The devices of this invention are electrical alternators. Typically these alternators are of a size suitable for use in automobiles and other conventional vehicles, but they are capable of use for many electrical generating purposes, for example stationary generators, power supplies for signage and the like, as is known in the art. They typically weigh a few pounds and have an electrical capacity of a few thousand watts. Such alternators have been used as battery charging units on production automobiles since the early 1960s. Since then, very little has been changed from that initial system other than to move the regulator element from a remote location to a location within the main alternator housing.
The two basic parts of such alternators are the magnetic field and the armature. The armature is the winding into which the generated voltage is induced. The magnetic field for alternators may be supplied in two ways, by an electromagnet or by a permanent magnet. In our invention the electric field is preferably supplied by a permanent magnet, but an electromagnet could be used. Permanent magnet construction provides numerous advantages in cost of construction, durability, and economy in use. However, permanent magnet alternators are not susceptible to control of the output voltage by control of the field winding current and voltage, as are alternators using electromagnets.
The present invention overcomes this obstacle and further improves on conventional alternator systems, including those using permanent magnet alternators.
The disclosed alternator system has the following advantages:
1. Lower cost of the alternator and associated equipment. PA1 2. The alternator is physically smaller, which permits installation in smaller spaces. PA1 3. The alternator is of lighter weight, which contributes to vehicle fuel economy. PA1 4. The alternator is more durable and rugged, which reduces repair costs and gives a longer service life. PA1 5. The system is more efficient (no field electrical power is required).
In the system of the invention the magneto-motive force is supplied by a permanent magnet or magnets. Thus, no slip rings or brushes are required to bring electrical power into the rotational (field) element. The permanent-magnet-powered magnetic circuit can be smaller and lower cost than the wound-rotor design. However, the magnetic circuit is not controllable. Since the field is not controllable, the invention achieves control of the system by use of unique controllable rectifier elements. The controllable rectifier elements may be coupled with suitable voltage regulating circuitry, as described herein.
As the state of charge of a battery in the system increases, its terminal voltage increases. In the system of the invention, the regulator circuit senses the battery terminal voltage. As the battery nears a fully charged state, one or more of the controllable rectifier elements is turned off for at least a portion of time. As the battery moves further from a nearly charged state to a fully charged state, more of the controllable rectifier elements are turned off for longer periods of time and the charging current is progressively reduced. This progressive decrease in charging current near the full-charge state is called taper charging. By using a plurality of controllable rectifier elements an effective taper charging may be achieved, as disclosed herein.
We are aware of the following U.S. patents, the disclosures of which are incorporated by reference herein:
3,341,763 3,508,095 3,553,511 3,568,037 3,586,956 3,601,688 3,601,688 3,713,015 3,766,463 3,723,844 4,740,739 4,806,812 5,191,256 5,633,576
It is an object of this invention to provide a permanent magnet alternator charging system for batteries.
It is an object of this invention to provide a charging system for batteries using permanent magnet alternators in which the charging output of the alternators is effectively controlled.
It is an object of this invention to provide a permanent magnet alternator and battery system which will function to self-charge a dead battery.
It is an object of this invention to provide an economical alternator and battery system.
It is an object of this invention to provide an efficient alternator and battery system.
It is an object of this invention to provide an alternator and battery charging system having an effective taper charging characteristic.
It is an object of this invention to provide a smaller and lighter weight alternator.
It is an object of this invention to provide a more durable alternator having a longer service life.
These and other objects of the invention will be apparent on review of the Description of the Preferred Embodiments and the Drawings.